mail.dnshigh.com has no CNAME records.
Question and response
Question
dig mail.dnshigh.com. NS
Answer
The response has no answer records.
Authority
dnshigh.com. 10800 SOA ns1.dnshigh.com. unixadmin.serverplan.com. 2026022704 86400 7200 3600000 14400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0